1. Field of the Invention
The present invention relates to a carriage for image scanning unit, an image scanning unit and a multifunction peripheral having an image scanning function. Specifically, the present invention relates to a technique to improve a luminous efficiency of a light source of the carriage for image scanning unit (hereinafter, a carriage for scanning an image will be simply referred to as a carriage).
2. Related Art
Conventionally, a multifunction peripheral (hereinafter, referred to as an MFP) provided with an image scanning function and an image forming function is known. Such an MFP is provided with a moveable carriage beneath a platen glass on which an original document is placed. An example of such a configuration is disclosed in Japanese Patent Provisional Publication No. P2004-214877A.
Typically, the carriage for scanning an image is provided with a reflecting plate for reflecting light emitted from a light source to illuminate the original document. The reflecting plate is arranged to surround the light source such that reflecting surface thereof faces the light source. As a result of this configuration, heat generated by the light source is accumulated in the reflecting plate, and further, radiation of heat of the light source is prevented. Therefore, the temperature of the light source is likely to increase. In particular, when a plurality of original documents are scanned continuously, or a relatively long time is spent for scanning an image at a high resolution, light emitting period becomes relatively long. In such a case, the temperature of the light source tends to increase extraordinary. There are light sources (e.g., a cold cathode tube) which have characteristics such that luminous efficiency is deteriorated as the temperature increase. When the luminous efficiency is deteriorated, the light intensity becomes insufficient, which may adversely effect image scanning.